This invention relates to the field of inspection, and more particularly, this invention relates to the field of inspecting containers such as cans with open tops.
Container inspection is becoming increasingly important as customers demand increased quality and lower cost products. The use of computers in the inspection process has increased these requirements. Some systems use computerized imaging systems. For example, one system uses a conversion of image data into binary values to search for defects. For example, U.S. Pat. No. 4,924,107 to Tucker discloses a system for inspecting cans where a plurality of horizontal regions on the inside surface of an object, such as an aluminum beverage can, are inspected. This system converts images to binary values and processes the values. Other systems have similar binary value algorithms.
Greater control, however, over the can inspection process in the internal areas of the can, such as near the top, are desired using similar metrology and grayscale analysis without complicated binary conversion algorithms.
The present invention is advantageous and provides non-contact, on-conveyor, real-time, 100% gauging and defect detection system for a container, such as beverage containers and cans. The system of the present invention identifies random production of anomalies that make cans rejectable and detects internal mechanical defects, surface defects, and contamination with foreign objects on the full 360xc2x0 interior of the can at line speeds to 3,000 CPM. Neck pucker, hole-in-sidewall, thumb dents, sidewall creases, ink stains and missing internal coatings can be determined and cans rejected if necessary.
In accordance with the present invention, the system inspects an object, such as a container or can, having an annular opening, and uses a plurality of cameras that acquire grayscale images of arcuate sectors that together comprise a circumferential area within the opening. A processor is connected to a plurality of cameras for receiving the grayscale images and determining defects within the container based on contrast differences in the grayscale intensity. Another camera can be positioned substantially above the opening for acquiring a top grayscale image of the opening. The processor determines defects in the top grayscale image and the grayscale images of arcuate sectors simultaneously.
In still another aspect of the present invention, a memory is associated with the processor for storing within a knowledge base of a computer memory the various rules for determining when a defect exists based on the contrast differences and grayscale intensity. The cameras can comprise charge coupled device (CCD) cameras. A strobe light is positioned at the inspection station for illuminating the container opening as containers are fed by a conveyor that advances a plurality of cylindrical containers along a redetermined path of travel into the inspection station.
An eject mechanism ejects a container from he conveyor after determining that any defects are serious enough to make the container defective. This object mechanism could comprise an air blow off mechanism.
In still another aspect of the present invention, the conveyor includes a vacuum assist mechanism to aid in retaining containers onto the conveyor by vacuum. A method is also disclosed for acquiring a plurality of grayscale images of arcuate surface sectors that together comprise a circumferential area inside the opening of the object and then processing the grayscale images to determine defects in the objects. The object can comprise the container, can or other object.